Ishikawa Diagram/ Fishbone diagram/ Cause and effect diagram

Ishikawa Diagrams

The Ishikawa diagrams are named after their inventor Kaoru Ishikawa professor of engineering at Tokyo University. It is a graphic tool that helps isolate a problem and display its causes. Thus, it’s also called as a cause-and-effect diagram or the fishbone diagram because of the way it looks. It explores the different causes that result in a single effect. The causes of the problem are arranged according to degree of significance in the fishbone diagram. An Ishikawa diagram is a good beginning to problem solving, as it pinpoints a problem, and shows the different causes to that problem. It is also an easy-to-use tool, which was designed so that an average person could easily follow it. Causes Causes of a fishbone diagram are usually determined during brainstorming sessions. Causes can be categorized as follows: In manufacturing industry Machinery Materials Methods Man power Measurements Management In the service industry People Processes Procedures Policies Product/Service Price Promotion Plant Surroundings Systems Skills Suppliers How to draw an Ishikawa diagram ? These steps to draw an Ishikawa diagram are Identify the problem - Write down the effect or problem, which is to be investigated, in a block on the left hand side of a large sheet of paper, and draw an arrow pointing to it as shown. This line forms the “backbone” of the fishbone diagram. Identify the major factors involved - The next step is to identify the factors that may be responsible for the problem. These could be any of the causes mentioned in the previous topic. However, one must make sure that the chalked out factors are really the causes and not symptoms of the problem. This step is usually done through brainstorming sessions among the group involved. The identified causes are drawn as lines off the spine. Identify the causes - Note down the possible causes of the factors identified in the previous step. Each factor may result due to many causes, thus this step requires a lot of brainstorming, so that all the crucial causes are identified. It is better to break down the more complex causes into multiple sub-causes. These causes can be shown by drawing lines off the bones in the fishbone diagram. Analyse the reasons for each cause - Behind every possible cause, there may be one or more reasons responsible for it. This step can be combined with the previous. The reasons for each cause must be brainstormed, identified and made note of until all possible reasons have likely been identified. Assess the fishbone diagram - The fourth step completes the fishbone diagram, following which the diagram can now be analyzed. Prioritize the causes according to their importance and for whom improvement actions can be developed. When is an Ishikawa diagram useful ? An Ishikawa diagram must be constructed if: There is a need to ascertain the root cause of a problem The areas of data collection must be identified There is a need to analyse all the possible reasons for the failure of an operation or a process